Braking mechanisms



June 4, 1963 R. w. CLAYTON ETAL 3,092,345

BRAKING MECHANISMS Filed Nov. 14, 1960 2 Sheets-Sheet l INVENTORS f/c/mol lMm ra/v 5 A0154 5.14000 June 1963 R. w. CLAYTON ETAL 3,092,345

BRAKING MECHANISMS 2 Sheets-Sheet 2 Filed Nov. 14, 1960 INVENTORI,fimm'a m (Z/rrrm/ 5 BY4AM6L E E a 50M United States Patent 3,092,345BRAKING MECHANISMS Richard W. Clayton, Toms River, and Arnel E. Jackson,Audubon, NJ., assignors to Radio Corporation of America, a corporationof Delaware Filed Nov. 14, 1960, Ser. No. 68,894 13 Claims. (Cl.242-5542 The present invention relates to braking mechanisms, and moreparticularly to a braking mechanism for use in a reeling system.

The invention is especially suitable for use in apparatus for handling areelable medium, such as a record tape. Apparatus for handling magneticrecord tapes is known as a tape transport.

In a tape transport, it is necessary, during braking, to apply morebraking torque to the reeling device which is supplying the tape than tothe reeling device which is taking up the tape. If the proper brakingtorques are not applied to the reeling devices, adequate tape tensionwill not be maintained and the tape will be reeled out of the supplyreeling device faster than it is taken up by the take-up reeling device.This causes the tape transport to throw loops of tape which can becometangled. On the other hand, tape tension should not be so great as tocause the tape to break or to stretch out of shape.

Another problem arises, during braking, when the reeling device whichsupplies the tape is emptied. It is then important to stop the take-upreeling device rapidly to prevent the end of the tape from whippingexcessively and tearing should it engage some part of the tapetransport.

Accordingly, it is an object of the present invention to provide animproved braking mechanism which will apply the braking torques to thereeling devices of a reeling system so that throwing of loops of themedium being reeled and damage to the medium is prevented.

It is a further object of the present invention to provide an improvedbraking mechanism in a reeling system which applies greater brakingtorque to the reeling device sup plying the medium being reeled than tothe reeling device which takes up the medium when it is Wound on boththe supply and the take-up reeling devices and which applies increasedbraking torque to the reeling device which takes up the medium when themedium is wound only thereon, as by being emptied from the supplyreeling device.

It is a still further object of the present invention to provide animproved braking mechanism which is simple to construct and has fewerparts than known braking mechanisms of the type which providedifferential braking action.

Briefly described, the invention includes a pair of brake bands whichare associated, separately, with a pair of reeling devices between whicha medium, such as a record tape, is adapted to be reeled. The brakebands are constructed to expand or contract under braking stresses. Arigid member is connected between one end of each of the brake bands.The other ends of the brake bands are each anchored. When the brakebands are brought into contact with the reeling devices, the rotationalenergy of the reeling device which supplies the tape is transmitted fromthe brake band associated therewith through the rigidband-interconnecting member to the other brake band which cooperateswith the reeling device which takes up the tape. The brake bandsassociated with the reeling devices which are supplying and taking upthe tape respectively expand and contract so that the bands and theinterconnecting member are displaced. The brake band associated with thetake-up reeling device is self-relieving since, in its displacedposition, less braking is applied, while the Patented June 4, 1963 icebrake band associated with the supply reeling device is self-energizingin its displaced position since more braking is applied. Differentialbraking action is therefore produced. Since greater braking torque isapplied to the supply reeling device than to the take-up reeling device,proper tension is maintained in the tape to prevent the throwing of tapeloops.

When the tape is emptied from the supply reeling device, or when thesupply reeling device is stopped, forces are no longer supplied throughthe rigid, band-interconnecting member to the brake band associated withthe take-up reeling device. Accordingly, the bands return to theirposition prior to displacement and full braking torque is applied to thetake-up reeling device. The take-up reeling device is then rapidlybrought to a stop. This minimizes the whipping and tearing of the endportion of tape as it is reeled onto the take-up reeling device. Thus,damage to the tape is prevented.

The invention itself, both as to its organization and method ofoperation, as well as additional objects and advantages thereof, willbecome more readily apparent from a reading of the following descriptionin connection with accompanying drawings, in which:

FIGURE 1 is a plan view showing a braking mechanism in accordance withthe invention, the brakes being disposed in released position;

FIGURE 2 is a view similar to FIG. 1, but showing the braking mechanismwith the brakes applied; and

FIGURE 3 is a fragmentary view of another form of brake mechanismaccording to the present invention.

Referring to the drawings, there is shown a pair of reeling devices 10and 11. These reeling devices include reel drive shafts 12 and 13 whichmay be driven by separate electric motors (not shown). Brake hubs 14 and15 are secured, respectively, to the shafts 12 and 13. Turntables 16(shown in phantom) are also attached to the shafts 12 and 13. Reels 17and 18 (shown in phantom) are adapted to be carried by the respectiveturntables. These reels carry a magnetic record tape 20. The tape isreeled between the reels along a path which extends past a tape guide19, a magnetic erase head 21, and a magnetic record-reproduce head 22,and also between a capstan 23 and a pressure roller 24. The heads 21 and22, the capstan 23 and the pressure roller 24 may be of the type wellknown in the magnetic recording and reproducing art. The capstan may bedriven by a separate drive motor (not shown), and the pressure rollermay be associated with a linkage (not shown) for the purpose of movingthe pressure roller towards the capstan to pinch the tape therebetween.This linkage may be designed in accordance with techniques known in themagnetic recording and reproducing art.

The motors which drive the shafts l2 and 13 are adapted to rotate inopposite directions and at different speeds. For either the recording orthe reproducing operation, the motor which drives the shaft 13 normallyrotates the shaft in a counterclockwise direction, as indicated by thearrow around it in FIG. I, at relatively slow speed to take up the tape20 as it is fed by the capstan and pressure roller arrangement from thereel 17 to the reel 18. The reel 17 therefore is normally the supplyreel and the reel 18 is normally the take-up reel. This terminology isused solely for purposes of convenience in description. The shaft 13,which drives the take-up reel 18, may also be driven at relatively highspeed in the counter-clockwise direction to rapidly wind the tapethereon. The latter operation is known in the art as fast forward feed."Alternatively, the shaft 12, which drives the supply reel 17, may bedriven at high speed in a clockwise direction, as indicated by the arrowaround shaft 12 in FIG. 2, for the purpose of rewinding the tape.

The brake mechanism according to the invention includes a brake band 25which cooperates with the brake hub 15 and another brake band 26 whichcooperates with the brake hub 14, the brake bands being disposed aroundat least part of their respective brake hubs. Each of these brake bandsis a spring member and may be constructed of annealed spring steel whichhas been hardened. The brake bands 25 and 26 have angular bends 27 and28 formed therein, respectively. These bends partake in providingself-energizing and self-relieving braking action and also smooth thebraking action to prevent breakage of the tape when the tape is stoppedas it is reeled at high speed during fast-forward or fastrewindoperations. The ends of the brake bands 25 and 26 near the bends 27 and28 therein are respectively anchored in blocks '29 and 30. These blocksmay be secured to the deck of the tape transport. A rigid bar 31interconnects the opposite ends of the brake bands 25 and 26. This baracts as a floating support between the opposite ends of the brake bandsand rests on stops 32 and 33 when the brakes are released, as shown inFIG. 1. A brake lining 34 is secured to the brake band 25, and a similarbrake lining 35 is secured to the brake band 26. A pair of brake bandstops 36 engages the back surface of the brake band 25 when the brakesare in release position, as shown in FIG. 1. Another pair of brake bandstops 37 serves a similar purpose in connection with the brake band 26.

Two springs 40 and 41 are connected, respectively, between the bar 31and brake pressure adjusting mechanisms 42 and 43. The bias of thesesprings 40 and 41 causes the brakes to be applied. The brakes aremaintained in released position by a rotary solenoid 44 having an arm 45secured thereto. This arm is pivotally secured to a brake rod 46 whichis fastened to the bar 31. When the solenoid is energized, the bias ofthe springs 40 and 41 is opposed and the brakes are maintained inreleased position, as shown in FIG. 1. Another spring 47 is connectedbetween the arm 45 and the bar 31 to eliminate play in the linkageincluding the arm 45 and the rod 46. Elimination of play results inquiet operation of the braking mechanism.

Each of the brake pressure adjusting mechanisms 42 and 43 includes aseparate L-shaped bracket 48 which is mounted on the tape deck, and ascrew 49 which is threaded into the associated bracket. The screws 49are respectively connected to the springs 40 and 41. The tension in thesprings 40 and 41 may be adjusted by locking the screws 49 in difierentpositions by means of nuts 50.

In operation, the solenoid is de-energized to apply the brakes.Referring to FIG. 2 and assuming, for the purpose of illustration, thata rewind operation is in process when the brakes are applied, the brakelinings 34 and 35 will then be forced under the bias of the springs 40and 41 into engagement with the brake hubs 14 and 15. Due to therotational energy of the reeling device 11, including the reel 18, thetape wound thereon, the hub 15, and the rotor of the motor coupled tothe shaft 13, a large inertia is developed. A torque due to this inertiawill be applied to the brake band 25 through the lining 34. This torqueeffectively expands or lengthens the band 25, since the bend 27 in theband 25 yields and tends to straighten. The brake band 25 thus becomeswrapped more tightly around the brake hub 15 and the braking torque onthe hub 15 is increased. In other words, a force is applied due to therotational energy of the reeling device 11 which aids the bias of thesprings 40 and 41 against the hub 15. Accordingly, greater brakingtorque is applied by the brake band 25 to the brake hub 15 of thereeling device 10, which is paying out the tape 20, than due to the biasof the springs 40 and 41 alone.

The force due to the rotational energy of the reeling device 11 is alsotransmitted through the bar 31 to the brake band 26. This force is in adirection to oppose the bias of the springs 40 and 41 so that thebraking torque developed due to the springs 40 and 41 against the hub 14is somewhat relieved. The bar 31 is displaced from right to left as seenin FIG. 2. The force \applied to the band 26 by the bar 31 effectivelycontracts or shortens the band 26 by increasing the angle of bend 28.The angle of the bend 28 is thereby decreased and the brake band '26recedes from the brake hub 14, whereby the lining 35 recedes somewhatfrom the brake hub. Accordingly, less braking torque than is due to thebias of the springs 40 and 41 alone is applied to the supply reelingdevice 10 which is taking up the tape during rewinding. The action ofthe braking mechanism is therefore self-relieving in the case of thereeling device which is taking up the tape and self-energizing in thecase of the reeling device which is paying out the tape. The brakingmechanism provided by the invention therefore accomplishes regenerativeand degenerative braking in a simple manner which requires relativelyfew parts as compared with known regenerativedegenerative brakingmechanisms.

Another feature of the braking mechanism provided by the invention isthat, as the reeling device which is paying out the tape is emptied, thebraking force thereon decreases while the braking force on the reelingdevice which is taking up or winding the tape increases. Moreover, whenthe reeling device which is paying out the tape stops, the full brakingforce due to the bias of the springs 40 and 41 is applied to the reelingdevice on which the tape is wound. The reeling device from which thetape is emptied will stop first, since it has less inertia than thereeling device on which the tape is completely wound. Accordingly, thebrake mechanism provided by the invention will apply full braking torqueto the reeling device on which the tape is entirely wound and will bringthat reeling device to a rapid halt. This counteracts whipping andtearing of the end of the tape as it dangles from the reeling device onwhich it is being wound.

In the case where the tape is being re-wound on the reeling device 10,which is the case discussed above, the inertia of the reeling device 11which is paying out the tape decreases as tape is unwound therefrom.Since the rotational force which is applied to the brake band 25 whenbrakes are applied and which is transmitted through the bar 31 to thebrake band 26 depends upon the rotational energy (inertia) in thereeling device 11, this force will decrease as the tape is unwound fromthe reel 18. Accordingly, the braking force on the reeling device 11will gradually decrease while the braking force 10 gradually increases.It will be remembered, however, that, so long as the reeling device 11is rotating, some force will be transmitted from the band 25 to the band26, so that regenerative and degenerative action will be maintained. Thereeling device 11 will come to a stop before the reeling device 10because of the lower inertia in the reeling device 11. As soon as thereeling device 11 stops, the force which is transmitted by way of thebar 31 to make the brake action on the reeling device 10 self-relievingdisappears. The full bias of the springs 40 and 41 is then applied tothe brake band 26. Increased brake torque is then applied to the brakehub 14 and the reeling device 10 comes to a stop rapidly. The reelingdevice 10 is stopped before the end of the tape can move and tearexcessively, as by being Whipped against the heads, guides or otherparts of the tape trans- The bends 27 and 28 provide smooth brakingaction since they absorb transients when the brakes are applied orreleased. The initial forces developed due to the rotational energy ofthe reeling device 10 or 11 causes the angles formed by one of the bends27 or 28 to increase while the angle formed by the other of the bends 27or 28 decreases. The transient motion of the bands 25 and 26 istherefore absorbed by the compression or expansion of the bends and thebands provide for smooth braking action. During fast forward windingoperating (i.e., from the reeling device to the reeling device 11), thesame action as described above takes place, but, of course, in thereverse direction.

Referring to FIG. 3, a modified form of braking mechanism adapted to beassociated with the brake hub 14 of the reeling device 10 is shown. Thismechanism is the same as shown in FIG. 1, except that a helical spring50 is secured at one end to the anchor block 30 and at its opposite endto the brake band 26 and the bend 28 is omitted. The spring 50 is atight spring and has spring characteristics similar to the bend 28. Theend of the brake band is therefore effectively anchored and fixed to theblock 30 as though the spring 50 were an integral part of the band 26.Expansion and contraction of this spring 50 will occur during braking,as explained in case of the bend 28. The bend construction may bepreferred, since the band 26 may be conveniently formed with the bend 28as an integral part thereof. A spring similar to the spring 50 may beassociated with the band 25, and the bend 27 therein may be omitted.

From the foregoing description, it will be apparent there has beenprovided an improved braking mechanism which provides degenerative andregenerative braking action. The mechanism also has features ofsimplicity of construction and operation not obtainable with knownregenerative or degenerative braking mechanisms. it will be appreciatedthat variations in the illustrated embodiments of the braking mechanismdescribed above, as well as other embodiments thereof, all within thescope of the invention, will become apparent to persons skilled in theart. Accordingly, the foregoing description should be taken merely asbeing illustrative and not in any limiting sense.

What is claimed is:

1. A brake mechanism for cooperation with a pair of rotatable reelingdevices comprising a pair of brake members disposed for brakingengagement with respective ones of said reeling devices, and a freelyfloating bar interconnecting said brake members and arranged forsimultaneously expanding one of said brake members and contracting theother of said brake members for providing differential braking when saidbrake members are applied in said braking engagement.

2. A brake mechanism for cooperation with a pair of reeling devicescomprising a pair of brake bands dis posed for braking engagement withrespective ones of said reeling devices, each having a braking portiondisposed around the periphery of a different one of said reelingdevices, one end of each of said braking portions being yieldablyanchored, and a freely floating bar interconnecting the other ends ofeach of said braking portions for simultaneously expanding one of saidbrake bands and contracting the other of said brake bands for providingdifferential braking when said brake bands are applied in said brakingengagement.

3. A brake mechanism for braking a pair of rotatable members betweenwhich a reelable medium is adapted to be reeled which comprises a firstbrake band around at least part of one of said rotatable members, asecond brake band around at least part of the other of said rotatablemembers, said brake bands each having a resilient, yieldable portion, afreely floating bar connecting the free ends of said bands to each otherand movable in op posite directions from one of said pair of rotatablemembers to the other, and means for moving said bar to engage said bandsin and disengage said bands from braking relationship with theirrespective said rotatable members, said yieldable portions being free toyield upon engagement of said bands in and disengagement of said brakebands from said braking relationship.

4. A brake mechanism for braking a pair of rotatable members "betweenwhich a reelable medium is adapted to be reeled which comprises a firstbrake band around one of said rotatable members, a second brake bandaround the other of said rotatable members, a freely floating barconnected to and between free ends of said bands and movable in oppositedirections from one of said pair of rotatable members to the other, andmeans for moving said bar without restraining its floating action toengage and disengage said bands from braking relationship with saidrotatable members.

5. A brake mechanism for cooperation with reeling devices between whicha tape is adapted to be reeled, said reeling devices having axes in acommon plane, said mechanism comprising a pair of bands of springmaterial each having an angular, resilient bend therein, means formounting said bands each around a different one of said reeling devices,said last-named means including means for fixedly mounting one end ofeach of said bands and a freely floating, rigid member connecting thefree ends of said bands, said rigid member being movable in oppositedirections from one of said devices to the other, and means for movingsaid rigid member in directions along a plane perpendicular to saidcommon plane for applying and releasing said brake bands.

6. A brake mechanism for cooperation with a pair of rotatable reelingdevices which comprises a pair of brake members which eliectively expandand contract separately disposed for lbralking engagement withrespective ones of said reeling devices, and a freely floating barinterconnecting said brake members movable in opposite directions fromone of said devices to the other for simultaneously expanding one ofsaid brake members and contracting the other of said brake members orvice versa when said brake members are disposed in said brakingengagement.

7. A braking mechanism for cooperation with a pair of reeling devicesbetween which a reelable member is adapted to be reeled, which mechanismcomprises a pair of brake members each separately disposed for braking adifferent one of said pair of reeling devices, a portion of each of saidbrake members being yieldable for expanding and contracting each of saidbrake members, and means comprising a freely floating memberinterconnecting said brake members and displaceable in oppositedircctions one for alternately expanding one of said members whilecontracting the other and vice versa.

8. A braking mechanism for cooperation with a pair of rotatable reelingdevices which comprises a pair of brake bands separately disposed aroundperipheries of different ones of said reeling devices, one end of eachof said bands being fixed, a freely floating bar connected to the freeends of said bands at opposite ends of said bar and movable in oppositedirections from one of said devices to the other, and effectivelyexpanding and contracting spring means constituting at least a portionof each of said bands.

9. A braking mechanism for cooperation with a pair of rotatable reelingdevices which comprises a pair of brake bands separately disposed aroundperipheries of difierent ones of said reeling devices, one end of eachof said bands being fixed, a bar connected to the free ends of saidbands at opposite ends of said bar, and effectively expanding andcontracting spring means constituting at least a portion of each of saidbands, said spring means comprising angular bends integral with saidbands.

10. The invention as set forth in claim 8 wherein said spring means arehelical springs having one end thereof effectively providing the fixedend of each of said bands.

11. A braking mechanism for a pair of rotatable, spaced reeling devicesbetween which a reelable medium is adapted to be reeled, which mechanismcomprises a pair of brake bands separately disposed adjacent theperipheries of different ones of said reeling devices, one end of eachof said brake bands being fixed, a rigid bar connecting the free ends ofsaid bands, portions of said bands being made of yieldable materialwhereby said bands alternately contract and expand when said bar movesin opposite directions, springs means for biasing said bar in adirection to move said bands into braking engagement with said reelingdevices, a rotary solenoid, and

means linking said solenoid and said her :for controlling 6 movement ofsaid bar.

12. A brake mechanism for cooperation with a pair of reeling devicescomprising a pair of brake bands of resilient material associatedseparately with each of said reeling devices, means for securing one endof each of said bands in a fixed position, and means for applying aregenerative braking force to one of said reeling devices whilesimultaneously applying a degenerative braking force to the other ofsaid reeling devices, said last named means including a freely floating,rigid mem ber interconnecting the opposite ends of each of said bandsand movable in opposite directions from one of said devices to theother.

13. A brake mechanism for cooperation with a pair of reeling devicescomprising a pair of brake bands associated respectively with each ofsaid reeling devices, a different resilient coupling between one end ofeach band and a fixed point, a freely floating, rigid memberinterconnecting the other ends of each of said bands and movable inopposite directions from one of said devices to the other, and means formoving said rigid member thereby to apply said bands in, and releasesaid bands from,

10 braking relationship with said device.

References Cited in the file of this patent UNITED STATES PATENTSSelsted Ian. 13, 1959 2,911,162 Kyle Nov. 3, 1959

1. A BRAKE MECHANISM FOR COOPERATION WITH A PAIR OF ROTATABLE REELINGDEVICES COMPRISING A PAIR OF BRAKE MEMBERS DISPOSED FOR BRAKINGENGAGEMENT WITH RESPECTIVE ONES OF SAID REELING DEVICES, AND A FREELYFLOATING BAR INTERCONNECTING SAID BRAKE MEMBERS AND ARRANGED FORSIMULTANEOUSLY EXPANDING ONE OF SAID BRAKE MEMBERS AND CONTRACTING THEOTHER OF SAID BRAKE MEMBERS FOR PROVIDING DIFFERENTIAL BRAKING WHEN SAIDBRAKE MEMBERS ARE APPLIED IN SAID BRAKING ENGAGEMENT.